diff --git a/docs/light_estimation_theory.md b/docs/light_estimation_theory.md index 672d75e..034a6aa 100644 --- a/docs/light_estimation_theory.md +++ b/docs/light_estimation_theory.md @@ -7,6 +7,27 @@ This document describes the **theory** behind using **normal passes** (from Open --- +## Exposure Analysis Methodology + +### Hybrid Approach +- **Display-Referred (IRE) Analysis** + - Direct sRGB luma values (0-100 IRE scale) + - Accurate for display-referred comparisons + - Matches what users see on their monitors + +- **Scene-Approximated (EV) Analysis** + - sRGB → Linear conversion (gamma 2.4 expansion) + - Reference: 18% gray @ 0.18 linear value + - ΔEV = log₂(linear_after / linear_before) + - Margin of error: ±0.3 stops due to gamma encoding + - Valid for relative exposure changes only + +### Accuracy Considerations +| Metric | Best For | Limitations | +|--------|----------|-------------| +| IRE | Display-referred analysis | Non-linear relationship to scene light | +| EV | Relative exposure changes | Approximate values from sRGB inputs | + ## 1. Inputs - **Normal Pass** (`N_rgb`): @@ -138,4 +159,3 @@ To implement this workflow in Python or node-based systems: - OpenGL and DirectX coordinate systems - Lambertian reflectance model - Image processing techniques for edge detection and frequency analysis -